1. Field of the Invention
The present invention relates to a liquid ejection device including a piezoelectric device.
2. Description of the Related Art
A piezoelectric device, which includes a piezoelectric layer having piezoelectricity to expand or contract along with increase or decrease of the intensity of an electric field applied thereto, and upper and lower electrode layers for applying the electric field to the piezoelectric layer, is used, for example, as an actuator in an inkjet marking head. The basic structure of the inkjet marking head includes an ink nozzle, which includes a pressurized liquid chamber (an ink chamber) and an ink ejection orifice, through which ink is ejected from the pressurized liquid chamber to the outside. Further, a diaphragm and the above-described piezoelectric device are attached to the ink nozzle. Typical piezoelectric materials used in conventional inkjet marking heads (hereinafter simply referred to as “head”) have a Curie point of at most about 140° C., and they are assumed to be used at the room temperature.
On the other hand, another type of actuator for use in a similar inkjet head proposed in Japanese Unexamined Patent Publication No. 2000-326506 includes a phase transition film that deflects along with phase transition of the crystal structure thereof, and a heating element for heating the phase transition film to a temperature around the Curie point, which is the phase transition temperature of the phase transition film. However, preferred piezoelectric materials disclosed in this patent document are those having a Curie point ranging from 50° C. to 90° C.
When electronic parts are mounted on a wiring board, electrode portions of the electronic parts are conventionally connected to the wiring pattern of the substrate through reflow soldering. In the reflow soldering, first, solder is fed to pads or lands of the wiring pattern on the wiring board. Then, the electronic parts are appropriately arranged on the pads or lands, and the substrate is heated in a reflow furnace to connect the electrode portions of the electronic parts to the wiring pattern. In the conventional reflow soldering, in order to feed the solder onto the substrate, cream solder is fed by screen printing through a metal mask.
The screen printing, however, is not suitable for precision printing.
Therefore, in order to carry out precision printing of the solder material, attempts have been made to use an inkjet printing technique to perform precision printing of the solder using the above-described inkjet marking head, and Japanese Unexamined Patent Publication No. 2005-161341 discloses a solder material for connecting electronic parts to a wiring board, which can be ejected using the inkjet printing technique.
Further, U.S. Patent Application Publication No. 20070134434 discloses a solder patterning method using an inkjet printing technique, which involves ejecting two or more types of metal pastes independently from each other onto a substrate, so that the solder composition of a formed solder pattern is adjusted by the ejected amount of each metal paste.
Since the conventional heads are assumed to mainly be driven at the room temperature, as described above, the methods proposed in the above Japanese Unexamined Patent Publication No. 2005-161341 and U.S. Patent Application Publication No. 20070134434 use a solder material or metal in the form of paste which can be ejected at the room temperature. These solder patterning methods using the inkjet printing technique necessitate heat treatment (reflow treatment) of the solder paste or the metal paste, which has been ejected and patterned on a substrate, to connect the electronic parts to the substrate.
During the heat treatment, the substrate having the electronic parts arranged thereon is heated to a temperature equal to or higher than the melting point of the solder, and this may damage the electronic parts.
Therefore, a means to achieve solder patterning which does not necessitate the heat treatment to connect electronic parts onto a substrate is desired.